My UV map has too many pieces
If you want to use seams, don't use "Smart UV Project" but "Unwrap". Smart UV project has the potential to split up into even more pieces than your seams showed based on geometry (the angle between faces), but "Unwrap" will simply use your seams. As far as the one vertex by itself, it was most likely not selected before the unwrap. Use A to select all, then do an Unwrap.